For example, as a known optical analysis apparatus, National Publication of International Patent Application No. 10-504397 discloses a sample analysis apparatus for optically measuring (inspecting) a sample disposed in a specific area of an analysis optical disc.
The sample analysis apparatus has an analysis optical disc which is a circular disc where particles (e.g., antibodies, blood plasma, and blood cells) are combined as a sample of a measured object. The disc comprises lower and upper layers, which are made of transparent plastic materials, and a metal foil layer having a light-reflecting surface between the layers. The sample analysis apparatus moves, relative to the circular disc, an inspection optical block disposed above the circular disc and an extraction optical block disposed below the circular disc, and measures the particles disposed in a specific area of the circular disc.
The inspection optical block is constituted of a laser diode, a lens for focusing a light beam, which has been emitted from the laser diode, on a surface of the circular disc, a polarizing prism for polarizing by 90 degrees a light beam having been reflected from the light-reflecting surface, and a detector for detecting reflected light which has been inputted via the polarizing prism.
The extraction optical block is constituted of a detector for extracting light (passing light) when a light beam having been emitted from the laser diode of the inspection optical block passes through the circular disc.
The emitted light beam is affected by the particles and passing light inputted to the detector of the extraction optical block is reduced in effect. Thus, the particles of the circular disc are detected by collecting and analyzing passing light inputted to the detector of the extraction optical block. Further, two-dimensional memory is provided for the radius direction and track direction of the circular disc, and a position where the particle is detected is marked and stored for each scan.
In the known optical analysis apparatus, by using the two-dimensional memory after measurements, particles serving as measured objects within a certain size range are selected from particles of various sizes in the specific area of the analysis optical disc and the number of detected particles is determined.
The following will describe an example where the number of particles ranging in size from three to six tracks is determined on the circular disc where particles ranging in size from three to seven tracks are disposed.
First, the two-dimensional memory is scanned by using a 3×A scanning window which corresponds to a particle of the minimum size, and particles having a size of three tracks are detected from the two-dimensional memory. Subsequently, the two-dimensional memory is scanned by using a 7×A scanning window which corresponds to a size which is one track larger than the maximum size of particles to be detected, and particles having a size of seven tracks are detected from the two-dimensional memory. “A” in the scanning window represents a size corresponding to a displacement of a detection position in the track direction. The displacement is caused by uneven rotation of the circular disc and uneven detection of signals.
However, particles ranging in size from three to six tracks cannot be correctly counted simply based on a difference between the number of detected particles having a size of three tracks and the number of detected particles having a size of seven tracks. This is because the number of detected particles having a size of three tracks includes the number of detected particles having a size of six tracks, which is a multiple of three tracks. Hence, it is necessary to scan the two-dimensional memory by using a 6×A scanning window corresponding to particles having a size of six tracks, which is a multiple of three tracks, and detect particles having a size of six tracks from the two-dimensional memory. By determining a difference between the number of detected particles having a size of seven tracks and the number of detected particles having a size of six tracks based on the number of detected particles having a size of three tracks, the true number of detected particles ranging in size from three to six tracks is determined.
In this way, when particles serving as measured objects within a certain size range are selected and the number of detected particles is determined, it is necessary to scan the same tracks having the particles again and again while frequently changing the size of the scanning window for selecting the particles, so that much time is spent in the detection and counting of particles and the particles cannot be counted correctly.